Stabilized crystal triode system



Dec. 22, 1953 A. H. REEVES ET AL STABILIZED CRYSTAL TRIODE SYSTEM Filed May 23, 1951 PULSE SOURCE /NPUT I n ventor MEC Fl- REEVES (Ha/1L5 0:5- WHITE Attorney Patented Dec. 22, 1953 UNITED sures OFFICE;

STABIEIZEDB GRY'STAL TRIODELISYSTEML Alec Harley. Reeves and Charles deBbi'smai'on White, liondon England,,. assi'gnors" to Inter national Standard Electric-Corporation; New

York, Ni-Y'l' ApplicatiomMay 23;; 1951, .Serial-N0.-227,7.98-

nrioritts';apmiceuimGreat-Beam 'May'31, 195m The present inventionrelatesto electric ampli fying devices employing semi-condhctors whmh have been calledcrystal triodes It is known to mount a crystal of germanium or other suitable semi-conductor in-aunetabbaseor holder with which itmakes contact-over a relatively large area; andto provide it with-twoelectrodes arranged close together in contact with the surface of the-crystal'. that. the surface of the crystal is suitably treated, and that a suitable el'ectroforming-process is applied to-the electrodes, the device (whichhas been called a 'crystal'tricde) can beoperated as an amplifierm which one of the electrodes (called the emitter electrode is an inputel ectrode, and the other (called'the collector elec trode) is an output electrode:

A preferred electroforming process-is described in the specification accompanying U; apphca um No. 156,4 2 filed March 18',- 195'O of KI Matthews-C. de B. White for Electric Semi-- Conductors.

Experience has shown that' some crystaltriodes in time tend tovary their performance, or to" become unstable, they may become noisy; and their characteristics may be affected by changes in humidity or temperature,- or by pi'clring up of electrical disturbances produced by sparking: ap

as not to interfere with the normal. operation. of.

the crystal triode, and ithas. been found that. the changes which tend" to. take. place. inthe.

characteristics and performance of the crystal triode are inhibited by the periodical application of the pulses.

simple means are also envisaged for simultaneously pulsing a large number of crystal triodes without causing any mutual interference between them, so that the additional cost of the pulsing arrangements spread over a large number of crystal triodes becomes unimportant.

The invention will be explained with reference to the accompanying drawing. In Fig. 1 a simple circuit is shown for applying pulses to stabilise a crystal triode when in normal operation as an amplifier, for example. Fig. 2 shows how a common pulsing source may be applied to stabilise simultaneously a large number of crystal triodes in normal operation.

Then provided In Eigi. 1: the-:crystali triode is: shown assccnn prising a; germanium: crystal (assumed: to; be.

of the N-typel; fixed in, a metalbaseor holder. 2 with: a. terminal. shank; 3.

filed. May 26, .1951 of: A.v T.. Starr et. a1-.. for: CrystallDiodes: and T-riodes= Signals: to: be;

amplified: are appliedthrougha transformer having its secondary winding: connected between? the emitterelectrode andthe: base electrode 3,, in series. with the. usual positive polarising,

source 1" for. theemitter. electrode. Amplified:

signals may be takenfrom a transformer. 8' hav-- ing its primary winding connected between the collector. electrodet. and the-base electrode 3,. in

series with the usual negative polarisingv sou-roe.

e for'the-collector electrode. This is the simplest possible-amplifying circuit. and can be taken to represent any desiredtype of. circuit.

According to one. embodiment of the invention, a-relay- It (or other. suitable switchpr trembler); isiprovided periodically to chargea capacitor. l i fromlasource l2 and to. discharge it between. the.emitterandcollector electrodes i and.5. If

Netype germanium is used, the source. I 2. should. preferably have its negative. terminal. connected.

of perhaps once per second, or it may be.con.--

nectedina self. interrupting circuit. or arranged to give. a. short train otrapidly. repeated pulses at periodic intervals, fcrexample, atrain 022e, pulses once per. minute,. or. caused. to. operate periodically in any known way. The capacity of, the capacitor might be of the order of micromicrofarads, and the potential of the source l2 might be of the order of a hundred volts. By avoiding the introduction of resistance in the discharge circuit of the capacitor i2, additional to that contributed by the crystal triode itself, the duration of the pulses applied to the electrodes 4 and 5 can be reduced to the order of A microsecond or less. It is found that in these circumstances the noise introduced by the operation of the relay H) is negligible, or becomes so after continuous application of the pulses for some time.

Small high frequency choke coils l3 and. I4 may be inserted if necessary in the signal circuits,

The emitter andr collecton electrodes are a designated. 4: and: 5;. and may-makev the. form: of sharply. pointed wires: or catswhiskers; or: these. electrodes may consist of: metal films orcoatings. suitably. deposited on.- small'. areas.- of. the. crystal. surface, as described. in theispecificationof U..S. applicationv No;.228,486

as shown, to prevent the short pulses from loss by being shunted through these circuits and producing noise therein.

It can be arranged so that by use of the values such as those already suggested, the capacitor l I will have a negligible effect on the operation of the crystal triode.

In Fig. 2 an arrangement for simultaneously pulsing a plurality of amplifier circuits is shown.

The elements of the amplifier circuit are the same as in Fig. l and have been given the same designation numbers. The pulsing arrangement includes a Source of pulses l generating very short pulses (perhaps with a duration of 500 microsecond) repeated at the rates already suggested. The pulses are supplied to a busbar circuit it to which are connected the primary windings of any number of pulse transformers l7, l8, I9 etc, one for each crystal triode to be stabilised. The transformer i3 is shown to have a secondary winding comprising two sections 2B, 21 of perhaps one turn each connected in series respectively with the emitter and collector electrodes =3, 5 of the crystal triode. The loop circuit is completed by a small capacitor 22, and the two sections in, El are connected series aiding round this loop. The transformer l6 should preferably be poled so that when N-type germanium is used, the initial and largest peak of the transient pulse current circulates round the loop so as to make the collector electrode 5 negative to the emitter electrode 4. The amplitude of the pulse should be just sufficient to maintain the stability of the crystal triode.

It will be understood that the transformers l1 and i9 (and any others, not shown, connected to the busbar circuit 16) will be arranged in corresponding crystal triode circuits in the same Way as the transformer 58. i'hus all the crystal triodes will be stabilised simultaneously from the single source Hi.

It is not essential to have both the secondary sections 25 and 2 1. One of them could be omitted.

Crystal triodes are rather susceptible to dampness, and are generally i'ound not to be very reliable or constant in operation unless they are enclosed in a hermetically sealed container. This greatly increases the cost, but it is found that an ordinary unenclosed crystal triode when pulsed in the manner described operates more reliably and with much less serious variation. The noise level is also reduced. It has also been found that the noise produced by a sealed crystal triode is reduced by periodic pulsing in the manner described.

Ir" P-type germanium is used in the crystal triode, the bias sources 2' and 9 and the source i2 in Fig. 1 will all need to be reversed, and also the poling of the transformers ii, i8, 19 etc., in Fig. 2.

It will be understood that although the circuits shown in Figs. 1 and 2 to illustrate the invention are amplifier circuits, the stabilising pulses could be supplied to a crystal triode employed as a modulator or demodulator, or as a rectifier, or in fact in any circuit in which signals are operated upon or otherwise translated. The crystal triode might also be employed as an oscillation generator, and the application of pulses in the manner described would suppress unwanted noises arisin from the crystal triode.

While the principles of the invention have been described above in connection with specific embodiments, and particular modifications thereof, it is to be clearly understood that this description is made only by way of example and not as a limitation on the scope of the invention.

What we claim is:

1. An electric circuit for translating signals, comprising a crystal triode having a base elec trade and emitter electrode and a collector electrode, separate blessing means between each of the emitter and collector electrodes and said base electrode, input means for applying the signals to be amplified to said emitter electrode, output means for deriving amplified signals from said collector electrode, a source of short stabilizing pulses, stabilizing means for applying said short stabilizing pulses between said collector and emit: ter electrodes, and means for suppressing said stabilizing pulses and blocking the application thereof to said base electrode, said last mentioned means comprising a first choke coil connected between said initter electrode and the input means, and a second choke coil connected between the said collector electrode and the output means.

2. A circuit according to claim 1 in which the said stabilising pulse source comprises means for periodically charging a capacitor and then discharging it between the said emitter and collector electrodes.

A circuit according to claim 1 in which the said stabilising means comprises a transformer having a primary winding connected to the said pulse source, and a secondary winding connected between the said emitter and collector electrodes.

i. A circuit according to claim 3 in which the said secondary winding is divided into two parts separated by a capacitor.

ALEC HARLEY REEVES. CHARLES or: B OISMAISON WHITE.

References Cited in the file of this patent UNITED STATES PATENTS Number 

